Twelve boys and their football coach trapped in a flooded Thai cave will have to squeeze through an extremely narrow tunnel in pitch blackness — the main “crisis” point that looms near the end of their treacherous escape bid.

Authorities have highlighted the tiny passageway near T-Junction, or Sam Yak in Thai, as the most dangerous element of the journey for the “Wild Boars” team that began Sunday morning, but there are many other potential pitfalls.

The rescue effort is likely to take two to three days to complete, Major General Chalongchai Chaiyakorn, an army commander, told reporters, adding it “depends on other factors like the weather”.

Here are some of the challenges that the boys and their coach will face leaving the cave they ventured into on June 23, becoming trapped more than four kilometres (2.4 miles) from the entrance because of monsoon rains.

Diving ability

The boys, aged from 11 and 16, have no diving experience and some can not even swim. They have…